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Thread: 7427 MPFI tuning

  1. #1
    Fuel Injected! JeepsAndGuns's Avatar
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    7427 MPFI tuning

    Now that I have everything on and running, now its off to tuning.
    Well first start was not that great, it cranked and died, had to keep my foot on it to keep it running, and according to my WB, I was lean, was around 15-16. So I tweaked my tables some and it didnt help much. But that was before I had my air filter on it, so I couldnt drive it, didnt really want to with it lean. I tweaked the tables some more and go it ok.
    Fast forward to when I now have a air filter/intake on. When doing my original injector calculations, the first calculator said at 40 psi, I should have been pretty much at where I was when my old tbi. But I found another one and it gave me diffrent numbers and I was too little flow. So I bumped my fuel pressure up to 45 psi and adjusted the injector flow in the bin to match. (I am running the vac refrenced FPR)
    Now I was able to drive, long story short, it has taken several drives, then fuel map tweeking to get me to where I am. my fuel maps are taking on a diffrent shape. First couple tuning sessions my BLM's were in the 150's, next few times were in the mid to high 140's, now I am down to the high 130's and low 140's. But its still staying there, and my main fuel map in the 90-100 map areas are up to 99.6, so I'm thinking mabey I need to bump the pressure up a couple more pounds?

    Odd thing though, according to my wideband, I am pretty much staying at about 13.5 afr all the time in closed loop (unless I am in PE or DFCO that is) Every now and then it comes up to 14.x, but then goes back down to around 13.5
    Also, when getting on the gas, like almost wot, the BPW can go as high 9.30 or so, it also turns red when it does this. Is this too high? Or is that simply set up for TBI, and it be ok for mpfi? I changed the fuel useage box on my dash to "inj DC %" Am I to assume that stands for injector duty cycle %? If so, it didnt seem to go much over 20.xx

    I will say, the engine has a almost completely diffrent sound to it. Both the sound of the engine, and the exhaust. Exhaust actually seems a little louder, has a diffrent note to it, kinda hard to discribe the diffrence. Even in dfco it sounds diffrent. Before, with the tbi, the engine just kinda went silent when in dfco, now you still hear exhaust noise, kinda has a slowing vrooooommmmmmm sound to it...lol
    As I have done more work to the fuel maps, it does seem to have some more pickup and go to it, pulls and revs quicker. From the sound and the way it acts now, its almost a completely diffrent engine.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  2. #2
    Super Moderator dave w's Avatar
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    I'm wondering if tweaking the injector flow in the .bin file might help? I usually get the injector flow figured out first, then work on the VE Tables. Generally speaking, I figure out an injector flow that makes everything all rich, and then figure out an injector flow that makes everything lean, then hopefully an injector flow somewhere in the middle will work. Quite often I actually end up with an injector flow that has some of the VE Rable lean, yet other parts of the VE Table Rich.

    I've come to the conclusion, What an injector actually flow ... What an injector is rated to flow ... and What the .bin file injector flow is set for ... is really apples / oranges / and bananas!

    hope this helps,
    dave w

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    EFI GearHead ! EagleMark's Avatar
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    Going to have to do some figuring on BPW and Injector Duty cycle to make it accurate in the ADX file as it was set for TBI, I don't know if it is accurate now with MPFI?

    Then just because it goes to red zone on BPW is where alarm is set, does not mean it's wrong. 9.xx is pretty high if it was accurate but OK at low RPM, as RPM rise the time allowed is shorter and shorter, that is where Injector Duty Cycle value with proper equations from BPW comes in and you need to stay under 85%.

    What Dave said is correct but you do need a starting point. How many HP approx will engine produce? What size injectors? Have injector offset VS battery voltage been set for those injectors? Then you can use a calculater to find fuel pressure needed to support HP and get a correct BPW/BPC in bin file. From there you can tweak injector flow a little up or down to get VE in ballpark. Shoot for under 90 and no higher then 95 in peak demand VE cells. If your injectors are GM for correct cubic inch engine with VFPR then 43.5 at idle and find BPW/BPC in MPFI bin.

    Here's a couple links with calculators for determining these settings before you start to tune.
    http://www.mindsciencemotorsports.com/graphics/tech.htm

    http://www.megamanual.com/v22manual/minj.htm

    http://www.bgsoflex.com/pwcomp.html

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
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  4. #4
    Fuel Injected!
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    if your wideband says 13:1 but your blms are still high, chances are your O2 constants need be lowered? assuming that your wideband has a free air cal and commanded CL afr is 14.73.

  5. #5
    Fuel Injected! JeepsAndGuns's Avatar
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    One problem, is I am absoultely clueless about how many HP my engine makes, or even how much it "should" make. All I can do is look up factory specs, and then list what I have done to the engine thats not stock. Anyone have desktop dyno? I have no clue what to set the bpw Vs voltage to, I have no specs to go by, and we touched on it a little on another thread and we figured it would probably be ok enough at the stock bin settings. The injectors are dodge neon 0280155703 injectors, they flow 238cc at 3 bar (22.66lbs/hr @ 43.5psi) But right now at 45 psi, they should be flowing roughly 23 lbs/hr.

    Going to have to do some figuring on BPW and Injector Duty cycle to make it accurate in the ADX file as it was set for TBI, I don't know if it is accurate now with MPFI?
    That was kinda my thoughts. The 9.xx bpw was when I was at pretty much wot and close to 4k rpm, pretty much the max I ever rev to.


    I have no ideas if this is correct. I just entered in my actual displacement (based on my .040 overbore) and put 4800 rpm as I never rev past that.

    Input Parameters Are the Following:
    • CID = 409
    • Volumetric Efficiency = 80%
    • Engine RPM = 4800
    • Number of cylinders = 8
    • # Injections per 2 Crank Revs = 2
    • Air/Fuel Ratio = 14.7
    • Test Injector Size (Lbs/hr) = 23
    Computation Results:

    • The Engine uses 1.811e-03 pounds of air during 2 crankshaft revolutions at the given VE of 80%, per cylinder.
    • For the desired Air/Fuel Ratio of 15, the Injector Fire Time is 9.6 milliseconds for one event (batch), 19.3 milliseconds total.
    • For an engine operating at 4800 revolutions per minute, the Maximum Opportunity for Injection is 25.0 milliseconds (per 2 Crank Revolutions), which yields a 77.1% Duty Cycle.


    if your wideband says 13:1 but your blms are still high, chances are your O2 constants need be lowered? assuming that your wideband has a free air cal and commanded CL afr is 14.73.
    Any more info on this? I am still a noob to all this.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  6. #6
    EFI GearHead ! EagleMark's Avatar
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    The injectors are dodge neon 0280155703 injectors, they flow 238cc at 3 bar (22.66lbs/hr @ 43.5psi) But right now at 45 psi, they should be flowing roughly 23 lbs/hr.
    This is going to be first issue, you really need the spec sheet on these to fill in Injector Offset Vs Battery.

    Since I've never done thisMPFI with 16197427 before and would like to learn can you post your bin, ADX and XDF so I can see what you have done and we are working on same page?

    I'll try and help with the rest while others chime in.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  7. #7
    EFI GearHead ! EagleMark's Avatar
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    One thing I noticed so far with your calculation is injector firing per revelution, see note below from $0E in flags "CPI/PFI Mode"

    Usage: Air Fuel Mode Words
    Tips: To change between TBI and CPI/PFI injector firing strategies. Checkmark if you will be using Central Port Injection or Port Fuel Injection. TBI fires the injectors twice per crankshaft revolution. CPI/PFI fires the injectors once per revolution. PCM modifications are also required.

    And "Synchronous Fuel At Idle " Tips: Checkmark to enable Synchronous Fuel At Idle. TBI only.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  8. #8
    EFI GearHead ! EagleMark's Avatar
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    The link in TBI to MPFI zip file is dead, I searched and found it and all the work that went into this, good read.

    http://www.fullsizechevy.com/forum/g...y-volts-2.html

    I'm assuming your read both docs in the TBI to MPFI Zip folder and have made the changes? If so I think your only stumbling block to getting good starting base settings is going to be the Injector Offsets Vs Battery voltage for those injectors.
    Attached Files Attached Files

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  9. #9
    EFI GearHead ! EagleMark's Avatar
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    Found a Bosch data information and has your injectors in it. Don't know if it is what is needed as I have never played with anything other then GM injectors which has all known settings for...
    Attached Files Attached Files

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  10. #10
    Fuel Injected!
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    If the OP would like , I can send you a copy of my '7427 $OE MPFI .bin I run with the 502/4L80E in my Dually , don't know if it'll help any or not , but might give some ideas.

    TOM
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    2006 Forest river-Sierra 37' 5th wheel
    1999 Astro Van, L31 Vortec , 4x4 conversion
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    1993 K-3500 "Ex-diesel" 454/4L80E - '7427
    1992 454SS "Eh Stock" , Blower & '7427 swap .
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    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
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  11. #11
    EFI GearHead ! EagleMark's Avatar
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    If it runs good I'd like to see it.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  12. #12
    Super Moderator dave w's Avatar
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    Here is a screen shot of some Edelbrock Pico Injectors (PN# 3574) running MPFI mode.

    dave w
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  13. #13
    Fuel Injected! JeepsAndGuns's Avatar
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    I read the MPFI zip file, and actually have a 0EMPFI bin file I got from another zip file from somewhere (mabey on here somewhere) I followed all instructions and entered in all values according to the zip file. I had the XLS file open and entered each one in, one at a time. I actually had that 0Empfi bin open in the "compare" and used that when I pulled up each value that needed changed according to the zip file. Each value listed in the zip matched the one in the 0Empfi bin, so I copied each one into my bin. Funny thing was, the injector offset Vs battery volts in that bin, was the same as the tbi values in my bin.

    Not sure about that xls file, I wouldnt know how to figure out that data if I wanted to.

    I will post up my bin as it is at this moment, and my adx file. I am using a unmodded 0E xdf, but will post it up too per request. I added -1 to the end of the adx file so anyone knows I changed it to the dash layout I wanted.

    I keep seeing people say to have the injectors tested. So, WHERE can I get this done? Looks like the chance of finding the offsets for these injectors is gonna be slim to none. I actually have 4 extra of these injectors I have as spares, as I am also using the exact same injectors in my YJ's 4.0, always goo to have spares. So if someone can give me name/address/phone number of a place or person who can test these and give me the correct offsets, I will mail them out to them ASAP!
    Attached Files Attached Files
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  14. #14
    EFI GearHead ! EagleMark's Avatar
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    Halin A$$ in the FullSizeChevy forum was going to build a flow bench and do some testing, he was asking for differant injectors. An injector service shop can flow check injectors. But since I've never done this before with unknown injectors I don't know what the answer is to what they are looking for?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  15. #15
    Fuel Injected! JeepsAndGuns's Avatar
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    I looked on google and this is prety much the only thing I found, other than threads in forums with people talking about injector offset vs battery volts.

    http://www.ielinc.com/fuel_injectors_web_site.pdf

    Looks like a big operation, wonder if they will do little jobs for the little man?
    Last edited by JeepsAndGuns; 04-10-2012 at 04:31 AM.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

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